(a) Field of the Invention
The present invention relates to a compound power mechanism and an electric bicycle, and more particularly to a compound power mechanism able to integrate brushless motor power with pedal power.
(b) Description of the Prior Art
These days, an electric bicycle is provided with a brushless motor instead of a brushed motor. The brushless motor is small in size and has high efficiency, and provides a multi-pole (10 to 32 poles) and low speed. During the development of electric bicycles, a hub motor is derived, such as disclosed in U.S. Pat. No. 3,921,741, U.S. Pat. No. 7,628,518, and U.S. Pat. No. 5,828,145. The hub motor is directly mounted on the front wheel or the rear wheel of a bicycle, without transmission of a chain. However, the hub motor has the problems that the hub motor makes the bicycle off-balance and that water can easily flow into the hub motor. Thus, the motor should be disposed at the center of the bicycle frame to overcome the shortcomings of the hub motor. The problem of the brushless motor applications is how to couple with pedal cranks for the electric bicycle to provide both motor power and pedal power without making the structure too complicated. For example, speed change of a gear box is not required so to lower the manufacture cost and power loss. Accordingly, the inventor of the present invention has devoted himself based on his many years of practical experiences to solve these problems.